1. Field of the Invention
The present invention relates to a peristaltic tube pump for discharging liquid by opening and closing spaces in a tube, and a tube used for the tube pump. More particularly, the present invention relates to a tube pump for continuously discharging a predetermined amount of liquid and a tube used for the tube pump.
2. Description of Related Art
In a typical tube pump, a flexible tube is squeezed by a roller, fingers or the like to sequentially change a position where the interior of the tube is opened and closed, so that liquid is sucked into, sequentially delivered through and discharged from the tube. The merit of such a tube pump is that the tube pump does not need to be sealed and therefore liquid is not accumulated in the tube pump.
Thus, such a tube pump has been widely used for printers, infusion pumps, detergent supply pumps and the like. In other words, the tube pump has been widely used in mass production factories, laboratories and the like as a pump for discharging and delivering various types of liquid such as medical fluid, electrolyte, additive and adhesive.
Typically, the tube pump is a roller-type tube pump in which liquid is delivered by squeezing a tube using a roller.
However, since the tube is strongly squeezed in the roller-type tube pump, the tube is considerably sagged or displaced. Consequently, discharge accuracy is hardly improved.
Thus, a finger-type tube pump has been suggested in which a tube is less sagged or displaced as compared to the roller-type tube pump so as to improve accuracy (for example, see Document 1: JP-A-9-256957).
In the finger-type tube pump, fingers are reciprocated in sequence to squeeze the tube, thereby delivering liquid.
However, in a typical tube pump, irrespective of a roller-type or finger-type tube pump, liquid discharge is suspended when a squeezed part of the tube reaches an outlet of the tube because liquid is delivered by sequentially squeezing a tube using a roller or fingers. Thus, in the tube pump, liquid usually cannot be continuously discharged because of the structure of the tube pump.
To solve such a problem, there has been a roller-type tube pump including two tubes and two rollers used for squeezing the tubes respectively. In this roller-type tube pump, when liquid is not discharged from one of the tubes, liquid is discharged from the other tube by shifting the positions of the rollers from each other. Thus, liquid can be continuously discharged.
On the other hand, in a finger-type tube pump, a plurality of fingers are required to squeeze one tube. Thus, two series of fingers are required for two tubes, so that the number of parts is increased and the size of the pump is also increased.
Because tubes are less damaged in a finger-type tube pump as compared to a roller-type tube pump, two tubes may be used for increasing a discharge amount in the finger-type tube pump. However, since a plurality of fingers are required for each tube, the number of parts and the size of the pump are increased as described above.
Consequently, a compact tube pump for discharging liquid using two tubes while retaining the advantage of being able to improve discharge accuracy and prevent damage of the tubes in a finger-type tube pump has been desired.